Twenty-six trials (with 2,546 participants) were included in the review; sample size ranged from 28 to 190 participants. Quality was described as generally good, although allocation concealment was unclear in many trials. No evidence of publication bias was found.
Pre-emptive incisional anaesthesia was superior to placebo for visual analogue scale (VAS) pain score at four hours (WMD -9.49, 95% CI -15.5 to -3.48; 10 trials) and 24 hours (WMD -4.75, 95% CI -8.9 to -0.6; 11 trials), but was not significantly superior to post-operative incision site infiltration.
Pre-emptive intraperitoneal local anaesthetic was significantly superior to placebo for VAS pain scores at four hours (WMD -5.76, 95% CI -11.27 to -0.25; 10 trials), eight hours (WMD -9.64, 95% CI -13.68 to -5.60; 13 trials), 12 hours (WMD -4.68, 95% CI -5.86 to -3.49; 12 trials) and 24 hours (WMD -5.57, 95% CI -8.35 to -2.79; 13 trials).
Pre-emptive intraperitoneal local anaesthetic was significantly superior to postoperative anaesthetic infiltration for pain scores at eight hours (WMD -7.42, 95% CI -13.4 to -1.45; six trials), 12 hours (WMD -7.27, 95% CI -10.26 to -4.28; five trials) and 24 hours (WMD -7.95, 95% CI -12.33 to -3.56; six trials). Results for other outcomes showed no statistically significant differences between groups.
Heterogeneity was present for all analyses of VAS pain scores (I2 60% to 91%); in most cases it was not explained by the pre-specified subgroup and sensitivity analyses.